The polyphenylene oxides and methods for their preparation are known in the art and are described in numerous publications, including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875. The Hay processes are based on the use of copperamine complexes. Manganese catalyzed methods for the preparation of polyphenylene oxides are disclosed in McNelis, U.S. Pat. No. 3,220,979; Olander, U.S. Pat. No. 3,956,242; Nakashio, U.S. Pat. No. 3,573,257; and Nakashio, U.S. Pat. No. 3,787,361.
In copending applications, Ser. No. 491,370, filed July 24, 1974 U.S. Pat. No. 3,956,424; U.S. Pat. No. 3,965,069; and U.S. Pat. No. 4,097,462, and disclosed various procedures for preparing polyphenylene oxides by the oxidative coupling of phenolic monomers. All of these patents are hereby incorporated by reference.
The prior art has employed .omega.-hydroxy oxime catalysts. The prior art types of .omega.-hydroxy oxime catalysts have been operable within a restrictive temperature range that precludes economic and practical operation of the processes at temperatures above 95.degree. F.
The optimum temperature range for most prior art manganese chelate catalysts is between 70.degree.-85.degree. F. Achieving this optimum temperature range is not practical in the type of commercial equipment usually employed in the preparation of polyphenylene oxides due to the inherent heat exchange limitations. Alternative methods of exotherm control such as slow monomer addition, oxygen limitation etc., are necessitated to permit operation below 90.degree. F. At temperatures above 95.degree. F., increasing the concentrations of manganese complexes such as the benzoin oxime manganese complexes fails to provide a process that will make high molecular weight polymer.
Catalyst deactivation is known to occur by several modes including in the case of manganese complexes of benzoin oximes base hydrolysis and/or isomerization of .alpha.-benzoin oxime to the inactive .beta.-isomer. The latter may accompany catalyst oxidation, but both deactivation mechanisms are thought to be accelerated at the higher temperatures. In addition, the interaction of molecular oxygen with the catalyst, perhaps forming an oxygen adduct, is generally more favored at lower temperatures.
The applicants have discovered that manganese complexes formed from phenyl benzoin oxime are more thermally stable and have an upper temperature limit that is 20.degree. to 25.degree. F. higher than a manganese complex of an .omega.-benzoin oxime at catalyst ratios of 1250:1 to 1500:1.
Accordingly, it is a primary object of this invention to provide a process for the preparation of polyphenylene oxide that utilizes a manganese complex catalyst that has a relatively high thermal stability.
It is a further object of this invention to provide a process for the preparation of a polyphenylene oxide that utilizes a manganese complex of phenyl benzoin oxime.